Objective: Patients with Idiopathic Normal Pressure Hydrocephalus are improved with shunt surgery. To increase the accuracy of the diagnosis, supplementary tests that characterize the cerebrospinal fluid (CSF) dynamics are used. The infusion test is one of these, used for shunt surgery selection and postoperative evaluation of shunt function. Forty-eight patients that had a preoperative investigation because of communicating hydrocephalus at the university hospitals in Umeå and Uppsala, Sweden, participated in the study. The purpose of this study was to evaluate a new method, with a new infusion protocol and new analysis methods, and compare it to the current method.